Prostaglandins are fatty acid derivatives composed of 20 carbon atoms with a 5-carbon ring. The name prostaglandin is derived from the prostate gland because the Swedish physiologist Ulf von Euler who first isolated prostaglandins in 1935 believed that they were secreted from the prostate gland. Now, it is known that they are ubiquitously found in mammalian tissues and metabolized rapidly after being synthesized from polyunsaturated fatty acids. Depending on the types thereof, the prostaglandins can stimulate the constriction of smooth muscle, or increase or decrease blood pressure or blood coagulation in some animals as well as promote ion transport across the membrane, stimulate inflammation and inhibit cardiovascular diseases and viral infection.
Meanwhile, prostaglandins and their homologues have short effective lives because they are chemically unstable and metabolized rapidly in vivo. It is not only because the active forms of prostaglandins and their homologues have hydroxyl and carboxyl groups, which are rapidly inactivated by enzymes, but also because their molecular weights are so low that they can be easily eliminated and excreted from the body (Narumiya S. et. al, 1999, Physiol. Rev., 79(4), 1193-1226).
Such chemical instability and short effective life of prostaglandins and their homologues have severely restricted their use for the treatment of respiratory, genitourinary, neurotic, endocrine and cardiovascular diseases.
In order to solve the above problems, therefore, extensive studies have been conducted to develop a pharmaceutically acceptable formulation of prostaglandins and their homologues, which can provide an improved stability, various methods of administration, an increased activity and a longer effective life. For example, Korean Patent No. 598,660 discloses 5-thia-ω-substituted phenyl-prostaglandin E derivatives, which are capable of binding strongly to prostaglandin receptors to produce an excellent activity; Korean Patent No. 850,133 discloses prostaglandin nitrooxy-derivatives having an improved pharmacological activity and enhanced tolerability; and Korean Laid-open Patent Publication No. 2001-0023839 discloses aromatic C16-C20-substituted tetrahydro-prostaglandins useful as FP agonists.
Meanwhile, the first step of the fast in vivo metabolism of prostaglandins, which results in their short physiological activity, is oxidation in which prostaglandins are inactivated by NAD+ dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH) (Ensor, C. M, & Tai, H. H., 1995, J. Lipid Mediator Cell Signalling 12:313-319).
15-PGDH, which was first extracted and isolated from placenta, lung and kidney, is localized in mammalian tissues (Krook M et. al., 1990, Biochemistry, 29, 738-743). Since 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is an enzyme that degrades prostaglandins, a large amount of prostaglandins are found in the tissues that do not express 15-PGDH. 15-PGDH oxidizes prostaglandin compounds containing a hydroxy group at the C-15 position to convert them into 15-ketoprostaglandins, thereby rendering these compounds biologically inactive (Tai H H et. al., 2002, Adv Exp Med Biol, 507, 245250).
According to the recent research results, it has been suggested that 15-PGDH plays a potential role in the carcinogenesis. The expression of 15-PGDH was found to be dramatically induced in the human prostate cancer cells treated by androgens as well as in the tumors derived from nude mice injected with human prostate cancer cells (M. Tong., 2000, Biochem. Biophys. Res. Commun., 276, 77˜81). Based on the above, many researchers expected that the suppression or the reduction of 15-PGDH expression could lead to the inhibition of carcinogenesis.
Accordingly, various researches for 15-PGDH inhibitors have been in progress, among which cyclooxygenase inhibitors, flavonoids, phytophenolic compounds and peroxisome proliferator-activated receptor γ (PPAR γ) were found to be effective in inhibiting 15-PGDH.
Under the circumstances, the present inventors have endeavored to develop a novel compound capable of inhibiting 15-PGDH and have found that novel thiazolidinedione derivatives having an excellent 15-PGDH inhibitory activity are effective in the stimulation of hair growth, the alleviation of cardiovascular diseases, gastrointestinal disorders and renal disorders, osteogenesis and wound healing.